Törnquist K
Endocrine Research Laboratory, University of Helsinki, Minerva Foundation Institute for Medical Research, Finland.
Endocrinology. 1992 Oct;131(4):1677-81. doi: 10.1210/endo.131.4.1396313.
In GH4C1 cells 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] has been shown to enhance the TRH- and bombesin-induced increase in intracellular Ca2+ ([Ca2+]i). The aim of the present study was to investigate whether this increase in [Ca2+]i could be due to enhanced release of sequestered Ca2+ in cells pretreated with 1,25-(OH)2D3. In digitonin-permeabilized cells, the addition of 10 microM inositol 1,4,5-trisphosphate (IP3) rapidly increased free Ca2+ ([Ca2+]) to 50 +/- 10 nM (mean +/- SE) in cells pretreated with 1 nM 1,25-(OH)2D3 for 24 h, compared with 25 +/- 5 in control cells (P < 0.05). Furthermore, stimulating permeabilized cells with TRH increased [Ca2+]. The increase in control cells was 20 +/- 2, compared with 55 +/- 11 in cells pretreated with 1,25-(OH)2D3 (P < 0.05). Repeated additions of IP3 resulted in an attenuation of the response of [Ca2+] in both control cells and cells pretreated with 1,25-(OH)2D3. However, only the first addition of IP3 resulted in an enhanced increase in [Ca2+] in cells pretreated with 1,25-(OH)2D3 compared with control cells. If the cells were stimulated first with TRH and then with IP3, no difference in the [Ca2+] response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Furthermore, if cells were stimulated with IP3 and then with TRH, no difference in the [Ca2+] response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Stimulating the permeabilized cells with thapsigargin resulted in an increase in [Ca2+]. However, no difference in the response was observed between control cells and cells pretreated with 1,25-(OH)2D3. Addition of GTP or the nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) had no effect on [Ca2+]. The results suggest that 1,25-(OH)2D3 has a modulatory effect on an IP3-sensitive intracellular Ca2+ pool in GH4C1 cells.
在GH4C1细胞中，已证明1,25 - 二羟基胆钙化醇[1,25-(OH)2D3]可增强促甲状腺激素释放激素（TRH）和蛙皮素诱导的细胞内钙离子浓度（[Ca2+]i）升高。本研究的目的是探讨[Ca2+]i的这种升高是否可能是由于用1,25-(OH)2D3预处理的细胞中储存钙离子的释放增强所致。在用洋地黄皂苷通透处理的细胞中，加入10微摩尔肌醇1,4,5 - 三磷酸（IP3）后，在1纳摩尔1,25-(OH)2D3预处理24小时的细胞中，游离钙离子浓度（[Ca2+]）迅速升高至50±10纳摩尔（平均值±标准误），而对照细胞中为25±5纳摩尔（P<0.05）。此外，用TRH刺激通透处理的细胞可使[Ca2+]升高。对照细胞中的升高幅度为20±2，而用1,25-(OH)2D3预处理的细胞中为55±11（P<0.05）。重复添加IP3导致对照细胞和用1,25-(OH)2D3预处理的细胞中[Ca2+]反应减弱。然而，仅首次添加IP3时，与对照细胞相比，用1,25-(OH)2D3预处理的细胞中[Ca2+]升高增强。如果细胞先用TRH刺激然后用IP3刺激，对照细胞和用1,25-(OH)2D3预处理的细胞之间在[Ca2+]反应上未观察到差异。此外，如果细胞先用IP3刺激然后用TRH刺激，对照细胞和用1,25-(OH)2D3预处理的细胞之间在[Ca2+]反应上也未观察到差异。用毒胡萝卜素刺激通透处理的细胞可使[Ca2+]升高。然而，对照细胞和用1,25-(OH)2D3预处理的细胞之间在反应上未观察到差异。添加鸟苷三磷酸（GTP）或不可水解的GTP类似物鸟苷5'-O-(3 - 硫代三磷酸)对[Ca2+]无影响。结果表明，1,25-(OH)2D3对GH4C1细胞中IP3敏感的细胞内钙离子池具有调节作用。
